Development of a deep learning-based error detection system without error dose maps in the patient-specific quality assurance of volumetric modulated arc therapy.

To detect errors in patient-specific quality assurance (QA) for volumetric modulated arc therapy (VMAT), we proposed an error detection method based on dose distribution analysis using unsupervised deep learning approach and analyzed 161 prostate VMAT beams measured with a cylindrical detector. For performing error simulation, in addition to error-free dose distribution, dose distributions containing nine types of error, including multileaf collimator (MLC) positional errors, gantry rotation errors, radiation output errors and phantom setup errors, were generated. Only error-free data were employed for the model training, and error-free and error data were employed for the tests. As a deep learning model, the variational autoencoder (VAE) was adopted. The anomaly of test data was quantified by calculating Mahalanobis distance based on the feature vectors acquired from a trained encoder. Based on this anomaly, test data were classified as 'error-free' or 'any-error.' For comparison with conventional approaches, gamma (γ)-analysis was performed, and supervised learning convolutional neural network (S-CNN) was constructed. Receiver operating characteristic curves were obtained to evaluate their performance with the area under the curve (AUC). For all error types, except systematic MLC positional and radiation output errors, the performance of the methods was in the order of S-CNN ˃ VAE-based ˃ γ-analysis (only S-CNN required error data for model training). For example, in random MLC positional error simulation, the AUC of our method, S-CNN and γ-analysis were 0.699, 0.921 and 0.669, respectively. Our results showed that the VAE-based method has the potential to detect errors in patient-specific VMAT QA.

Applying Artificial Neural Networks to Develop a Decision Support Tool for Tis-4N0M0 Non-Small-Cell Lung Cancer Treated With Stereotactic Body Radiotherapy.

PURPOSE: Clear evidence indicating whether surgery or stereotactic body radiation therapy (SBRT) is best for non-small-cell lung cancer (NSCLC) is lacking. SBRT has many advantages. We used artificial neural networks (NNs) to predict treatment outcomes for patients with NSCLC receiving SBRT, aiming to aid in decision making. PATIENTS AND METHODS: Among consecutive patients receiving SBRT between 2005 and 2019 in our institution, we retrospectively identified those with Tis-T4N0M0 NSCLC. We constructed two NNs for prediction of overall survival (OS) and cancer progression in the first 5 years after SBRT, which were tested using an internal and an external test data set. We performed risk group stratification, wherein 5-year OS and cancer progression were stratified into three groups. RESULTS: In total, 692 patients in our institution and 100 patients randomly chosen in the external institution were enrolled. The NNs resulted in concordance indexes for OS of 0.76 (95% CI, 0.73 to 0.79), 0.68 (95% CI, 0.60 to 0.75), and 0.69 (95% CI, 0.61 to 0.76) and area under the curve for cancer progression of 0.80 (95% CI, 0.75 to 0.84), 0.72 (95% CI, 0.60 to 0.83), and 0.70 (95% CI, 0.57 to 0.81) in the training, internal test, and external test data sets, respectively. The survival and cumulative incidence curves were significantly stratified. NNs selected low-risk cancer progression groups of 5.6%, 6.9%, and 7.0% in the training, internal test, and external test data sets, respectively, suggesting that 48% of patients with peripheral Tis-4N0M0 NSCLC can be at low-risk for cancer progression. CONCLUSION: Predictions of SBRT outcomes using NNs were useful for Tis-4N0M0 NSCLC. Our results are anticipated to open new avenues for NN predictions and provide decision-making guidance for patients and physicians.

CT Findings and Treatment Outcomes of Ground-Glass Opacity Predominant Lung Cancer After Stereotactic Body Radiotherapy.

BACKGROUND: Stereotactic body radiotherapy (SBRT) has been rapidly evolving and increasingly performed in patients with ground-glass opacity (GGO) predominant lung cancer (GGOp-LC). PURPOSE: To evaluate early-phase CT findings of GGOp-LC after SBRT. MATERIALS AND METHODS: Patients with GGOp-LC staged as cTis-2bN0M0 treated with SBRT were retrospectively identified. The CT images were analyzed using radiologists' interpretation and CT-density histograms. Long-term treatment outcomes were also assessed. RESULTS: This study evaluated 126 patients with 133 cases of GGOp-LC, comprising GGOp-LC with pure GGO (pureGGO-LC) (n = 31) and part-solid tumors (partsolid-LC) (n = 102). The median follow-up duration was 64.3 months (range, 10.8-178.9 months). Most GGOp-LC cases were interpreted as stable disease at 1 and 3 months after SBRT (96% [125/130] and 85% [62/73], respectively). However, the solid component was often interpreted as progressive disease (42% [34/82] and 60% [29/48], respectively). The GGO component was interpreted as denser in 47% (61/130) and 86% (63/73) of cases, respectively. For 25 evaluable pureGGO-LC cases at 3 months, the median tumor density values increased over time (P < .001). For 48 evaluable partsolid-LC cases at 3 months, the median areas of CT-density ≥ -160 HU increased over time (P < .001). The 5-year overall survival for GGOp-LC patients was 78.0%. No local or regional recurrence were observed. CONCLUSION: Clinical outcomes of SBRT for GGOp-LC were excellent, without local or regional recurrence. In the interpretation of early-phase follow-up CT scans of GGOp-LC after SBRT, it should be noted that most GGOp-LC remains stable disease, solid component increases in size, and GGO component is denser.

Feasibility of marker-less stereotactic body radiotherapy for hepatocellular carcinoma.

BACKGROUND: The feasibility of marker-less stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) has not yet been established, and, thus, was examined in the present study. MATERIAL AND METHODS: We retrospectively investigated patients who received marker-less SBRT for locally untreated HCC tumors between July 2005 and December 2018. Radiotherapy planning CT was performed under fixation with vacuum cushions and abdominal compression. The clinical target volume (CTV) was equivalent to the gross tumor volume (GTV). The internal target volume (ITV) margin to CTV was determined from calculations based on the motion of the diaphragm. The planning target volume (PTV) margin to ITV was 5-6 mm. In the set-up, radiotherapy planning CT and linac-integrated cone-beam CT performed in the same imaging and fixation settings were merged by referring to the anatomical components surrounding target tumors. The primary endpoint was the 3-year cumulative local tumor progression rate. The upper limit of the 95% confidence interval for the 3-year cumulative local tumor progression rate was less than 7.0%, which was interpreted as favorable local control and feasible for marker-less SBRT. Local tumor progression was assessed by mRECIST. RESULTS: We reviewed 180 patients treated with 35-40 Gy/5 fractions. The median follow-up time for the local tumor progression of censored tumors was 32.3 months (range, 0.3-104). The 3-year cumulative local tumor progression rate was 3.0% (95% CI, 1.1-6.5%). The 3-year overall survival rate was 71.6% (95% CI, 63.5-78.2%). Regarding acute hematologic toxicities, grade 3 hypoalbuminemia and thrombocytopenia were detected in 1 (0.6%) and 5 (2.9%) patients, respectively. Treatment-related death from SBRT was not observed. SBRT was initiated within 7 days after radiotherapy planning CT for 84% (152/180) of patients. CONCLUSIONS: Marker-less SBRT for HCC achieved favorable local control that fulfilled the threshold. This result suggests that marker-less SBRT with appropriate settings is a feasible treatment strategy.

Error detection model developed using a multi-task convolutional neural network in patient-specific quality assurance for volumetric-modulated arc therapy.

PURPOSE: In patient-specific quality assurance (QA) for static beam intensity-modulated radiation therapy (IMRT), machine-learning-based dose analysis methods have been developed to identify the cause of an error as an alternative to gamma analysis. Although these new methods have revealed that the cause of the error can be identified by analyzing the dose distribution obtained from the two-dimensional detector, they have not been extended to the analysis of volumetric-modulated arc therapy (VMAT) QA. In this study, we propose a deep learning approach to detect various types of errors in patient-specific VMAT QA. METHODS: A total of 161 beams from 104 prostate VMAT plans were analyzed. All beams were measured using a cylindrical detector (Delta4; ScandiDos, Uppsala, Sweden), and predicted dose distributions in a cylindrical phantom were calculated using a treatment planning system (TPS). In addition to the error-free plan, we simulated 12 types of errors: two types of multileaf collimator positional errors (systematic or random leaf offset of 2 mm), two types of monitor unit (MU) scaling errors (±3%), two types of gantry rotation errors (±2° in clockwise and counterclockwise direction), and six types of phantom setup errors (±1 mm in lateral, longitudinal, and vertical directions). The error-introduced predicted dose distributions were created by editing the calculated dose distributions using a TPS with in-house software. Those 13 types of dose difference maps, consisting of an error-free map and 12 error maps, were created from the measured and predicted dose distributions and were used to train the convolutional neural network (CNN) model. Our model was a multi-task model that individually detected each of the 12 types of errors. Two datasets, Test sets 1 and 2, were prepared to evaluate the performance of the model. Test set 1 consisted of 13 types of dose maps used for training, whereas Test set 2 included the dose maps with 25 types of errors in addition to the error-free dose map. The dose map, which introduced 25 types of errors, was generated by combining two of the 12 types of simulated errors. For comparison with the performance of our model, gamma analysis was performed for Test sets 1 and 2 with the criteria set to 3%/2 mm and 2%/1 mm (dose difference/distance to agreement). RESULTS: For Test set 1, the overall accuracy of our CNN model, gamma analysis with the criteria set to 3%/2 mm, and gamma analysis with the criteria set to 2%/1 mm was 0.92, 0.19, and 0.81, respectively. Similarly, for Test set 2, the overall accuracy was 0.44, 0.42, and 0.95, respectively. Our model outperformed gamma analysis in the classification of dose maps containing a single type error, and the performance of our model was inferior in the classification of dose maps containing compound errors. CONCLUSIONS: A multi-task CNN model for detecting errors in patient-specific VMAT QA using a cylindrical measuring device was constructed, and its performance was evaluated. Our results demonstrate that our model was effective in identifying the error type in the dose map for VMAT QA.

Fatal case of pancreatic panniculitis caused by occult neuroendocrine tumor in the corresponding organ: A case report and review of the published work.

Pancreatic panniculitis (PP) is a rare clinical variant of subcutaneous fat necrosis, developing in patients with a variety of pancreatic diseases such as acute or chronic pancreatitis, tumors and cysts. The tumor-associated PP represents a noteworthy skin manifestation of underlying internal malignancies, also known as dermadrome. Among causative pancreatic tumors, acinar cell carcinoma is the most frequent malignancy; however, little is known about how the origin of tumor cells and progression stage of pancreatic tumors potentially contribute to the establishment of panniculitis. Here, we present a 69-year-old Japanese male case of clinically aggressive PP on the bilateral legs, whose skin lesions developed prior to the diagnosis of occult pancreatic tumor and liver metastasis. Moreover, the immunopathology of the pancreatic lesion revealed neuroendocrine tumor (NET), a rare pathological variant. Skin lesions immediately spread to the upper limbs with extensive ulcerations and necrosis, accompanied by high levels of serum lipase and elastase, but not with other pancreatic enzymes. He died 2 months after the initial development of the skin lesion due to rapid deterioration of general condition. We reviewed 14 cases, including ours, of PP with NET in the pancreas thus far reported, to identify the clinicopathological characteristics regarding to what extent this rare complication could reflect the clinical course of pancreatic tumors and overall prognosis. Our published work review found that the disease has a significant male predominance (male : female, 13:1) and cases with occult pancreatic tumors died within 4 months after the development of their skin lesions. Our case was the poorest prognostic outcome. This report emphasizes that dermatologists should recognize PP with NET, reflecting a fatal prognosis, and to make a prompt diagnosis.

Multicenter prospective study of stereotactic body radiotherapy for previously untreated solitary primary hepatocellular carcinoma: The STRSPH study.

AIM: To prospectively evaluate the efficacy and safety of stereotactic body radiotherapy (SBRT) for patients with previously untreated solitary primary hepatocellular carcinoma (HCC). METHODS: The main eligibility criteria included the following: (1) primary solitary HCC; (2) no prior treatment for HCC; (3) Child-Turcotte-Pugh score of seven or less; and (4) unsuitability for or refusal of surgery and radiofrequency ablation (RFA). The prescribed dose of SBRT was 40 Gy in five fractions. The primary endpoint was 3-year overall survival (OS); the secondary endpoints included local progression-free survival (LPFS), local control (LC), and adverse events. The accrual target was 60 patients, expecting a 3-year OS of 70% with a 50% threshold. RESULTS: Between 2014 and 2018, 36 patients were enrolled; enrollment was closed early because of slow accrual. The median tumor size was 2.3 cm. The median follow-up at the time of evaluation was 20.8 months. The 3-year OS was 78% (95% confidence interval [CI]: 53%-90%). The 3-year LPFS and LC proportion were 73% (95% CI: 48%-87%) and 90% (95% CI: 65%-97%), respectively. Grade 3 or higher SBRT-related toxicities were observed in four patients (11%), and grade five toxicities were not observed. CONCLUSIONS: This study showed acceptably low incidence of SBRT-related toxicities. LC and OS after SBRT were comparable for previously untreated solitary HCC for patients unfit for resection and RFA. Although a definitive conclusion cannot be drawn by this study, the promising results indicate that SBRT may be an alternative option in the management of early HCC.

A Multi-Institutional Retrospective Study of Repeated Stereotactic Body Radiation Therapy for Intrahepatic Recurrent Hepatocellular Carcinoma.

PURPOSE: Through this multi-institutional study, we aimed to retrospectively evaluate the safety and efficacy of repeated stereotactic body radiation therapy (SBRT) for intrahepatic recurrent hepatocellular carcinoma (HCC). METHODS AND MATERIALS: Between 2005 and 2017, 709 patients with 835 HCCs underwent SBRT; those treated with repeated SBRT were eligible. The median prescribed dose was 40 Gy in 5 fractions. RESULTS: Eighty-one patients with 189 tumors underwent repeated SBRT (≥ 2 courses [median 2 times; range, 2-5 times]). The median follow-up periods from the first to the second SBRT were 41.5 (range, 12-99) and 20 (range, 1-81) months, respectively. The median interval between the first and second SBRT was 18 (range, 3-74) months. The 5-year local recurrence rate was 6.3% (95% confidence interval [CI], 2.3%-13.4%). The 5-year overall survival (OS) and liver-related death rates from the first SBRT were 60.4% (95% CI, 47.0%-73.8%) and 32.9% (95% CI, 20.3%-46.0%), respectively, and the 3-year rates from the second SBRT were 61.0% (95% CI, 49.9%-75.2%) and 34.5% (95% CI, 20.6%-48.9%), respectively. The frequency of grade 3 toxicity was not significantly different between the first and second SBRT (first: 11% [95% CI, 5.2%-20%]; second: 15% [95% CI, 7.9%-24%]; P = .48). Among 39 patients with no intrahepatic recurrence for 1 year after the first and second SBRT, the deterioration in liver function after the first and second SBRT was not significantly different; the albumin-bilirubin score increased 1 year after the first versus second SBRT (first, 0.143 ± 0.23; second, 0.195 ± 0.38; P = .48). Multivariate analysis revealed that the intrahepatic recurrence-free interval was the only significant factor for OS. CONCLUSIONS: Repeated SBRT for intrahepatic recurrent HCC resulted in high local control with safety and a satisfactory OS comparable with that of other curative local treatments for patients with well-preserved liver function.

Error detection using a convolutional neural network with dose difference maps in patient-specific quality assurance for volumetric modulated arc therapy.

The aim of this study was to evaluate the use of dose difference maps with a convolutional neural network (CNN) to detect multi-leaf collimator (MLC) positional errors in patient-specific quality assurance for volumetric modulated radiation therapy (VMAT). A cylindrical three-dimensional detector (Delta4, ScandiDos, Uppsala, Sweden) was used to measure 161 beams from 104 clinical prostate VMAT plans. For the simulation used error-free plans plus plans with two types of MLC error were introduced: systematic error and random error. A total of 483 dose distributions in a virtual cylindrical phantom were calculated with a treatment planning system. Dose difference maps were created from two planar dose distributions from the measured and calculated dose distributions, and these were used as the input for the CNN, with 375 datasets assigned for training and 108 datasets assigned for testing. The CNN model had three convolution layers and was trained with five-fold cross-validation. The CNN model classified the error types of the plans as "error-free," "systematic error," or "random error," with an overall accuracy of 0.944. The sensitivity values for the "error-free," "systematic error," and "random error" classifications were 0.889, 1.000, and 0.944, respectively, and the specificity values were 0.986, 0.986, and 0.944, respectively. This approach was superior to those based on gamma analysis. Using dose difference maps with a CNN model may provide an effective solution for detecting MLC errors for patient-specific VMAT quality assurance.

Stereotactic body radiotherapy for patients with non-small-cell lung cancer using RapidArc delivery and a steep dose gradient: prescription of 60% isodose line of maximum dose fitting to the planning target volume.

We retrospectively investigated outcomes, including pulmonary toxicities, of stereotactic body radiation therapy using RapidArc and a risk-adapted 60% isodose plan for early-stage non-small-cell lung cancer patients. We evaluated patients staged as cT1a-2bN0M0 between 2011 and 2017 and treated with a total dose of 40-60 Gy in five fractions to the 60% isodose line of the maximum dose encompassing the planning target volume with curative intent. Comorbidities and age were rated using an age-adjusted Charlson comorbidity index (AACCI). Factors associated with overall survival (OS) were investigated. A total of 237 patients with 250 lesions were eligible. The median follow-up was 28.0 months. The local recurrence rate at 3 years was 0.8%; none of the patients developed isolated local recurrence. OS, deaths from lung cancer, and deaths from intercurrent disease at 3 years were 72.7%, 8.2% and 19.1%, respectively. On multivariate analysis for correlating factors with OS, AACCI and maximal standardized uptake value on [18F]-fluorodeoxyglucose positron emission tomography/computed tomography remained significant. Grade ≥3 toxicities were limited to radiation pneumonitis in six (2.4%) patients (Grade 3 in four patients and Grade 5 in two patients). Among those, three patients had idiopathic interstitial pneumonia. The total dose was unrelated to the incidence of Grade ≥3 radiation pneumonitis (P = 0.69). Using the 60% isodose prescription and RapidArc, maximal local control was achieved with acceptable toxicities. Although the OS may depend on patient background, dose escalation aiming at higher local control can be beneficial for medically inoperable patients.

Clarithromycin mitigates radiation pneumonitis in patients with lung cancer treated with stereotactic body radiotherapy.

BACKGROUND: Radiation pneumonitis is a critical pulmonary toxicity after irradiation of the lung. Macrolides including clarithromycin (CAM) are antibiotics. They also have immunomodulatory properties and are used to treat respiratory inflammatory diseases. Radiation pneumonitis has similar pathology to them. Adverse reactions to macrolides are few and self-limited. We thus administered CAM to patients with high-risk factors for radiation pneumonitis, and retrospectively investigated whether CAM mitigated radiation pneumonitis following stereotactic body radiotherapy (SBRT). METHODS: Among consecutive patients treated with SBRT, we retrospectively examined lung cancer patients treated with a total dose of 40-60 Gy in 5-10 fractions and followed ≥6 months. Since January 2014, CAM has been administered in patients with pretreatment predictable radiation pneumonitis high-risk factors, including idiopathic interstitial pneumonias (IIPs), and elevated Krebs von den Lungen-6 (KL-6) and/or surfactant protein D (SP-D), and in patients developing early onset radiation pneumonitis. RESULTS: Five hundred and eighty eligible patients were identified and divided into 445 patients during the non-CAM-administration era (non-CAM-era) (before December 2013) and 136 patients during the CAM-administration era (CAM-era) (after January 2014). Median follow-up durations were 38.0 and 13.9 months, respectively. The rates of radiation pneumonitis ≥ grade 2 and ≥ grade 3 were significantly lower in CAM-era (grade ≥2, 16% vs. 9.6%, P=0.047; grade ≥3, 3.8% vs. 0.73%, P=0.037). For patients with the pretreatment predictable high-risk factors, the rate of radiation pneumonitis ≥ grade 3 was significantly lower, and that of grade ≥2 had a lower tendency (grade ≥3, 7.2% vs. 0%, P=0.011; grade ≥2, 21% vs. 9.6%, P=0.061). For patients developing early onset radiation pneumonitis, the rate of radiation pneumonitis ≥ grade 3 was also significantly lower (23% vs. 0%, P<0.05). Multivariate analysis revealed that dose-volumetric factor, the pretreatment predictable high-risk factors and non-CAM-administration era were significantly associated with or trended toward radiation pneumonitis ≥ grade 2 and ≥ grade 3. CONCLUSIONS: CAM mitigated radiation pneumonitis following SBRT. The efficacy of CAM should be confirmed in prospective studies.

Stereotactic body radiotherapy for lung cancer patients with idiopathic interstitial pneumonias.

PURPOSE: To compare toxicity and survival after stereotactic body radiotherapy (SBRT) between lung cancer patients with or without idiopathic interstitial pneumonias (IIPs), and to investigate the potential value of SBRT for the patients. METHODS: Among lung cancer patients receiving SBRT between 2005 and 2016, we evaluated those treated with a total dose of 40-60Gy in five fractions with curative intent who either were staged as cT1-4N0M0 or experienced postoperative isolated local recurrence. We analyzed the incidence of radiation pneumonitis (RP) in all patients and local recurrence and overall survival (OS) in T1a-2a patients. RESULTS: A total of 508 patients were eligible, including 42 with IIPs. The median follow-up was 32.3 (6.0-120.9) months. Significantly more patients with IIPs had grade ≥3RP than did those without IIPs (12% vs. 3%, p=0.009). The 2-year local recurrence rate was low in both groups (3.4% vs. 5.6%, p=0.38). The 2-year OS rate was significantly lower in the patients with IIPs (42.2% vs. 80.9%, p<0.001), although death from lung cancer was comparable (p=0.74). CONCLUSION: SBRT achieved excellent local control with acceptable pulmonary toxicity in lung cancer patients with IIPs. SBRT can be a reasonable option for early lung cancer patients with IIPs.

Stereotactic body radiotherapy for operable early-stage non-small cell lung cancer.

PURPOSE: To analyze outcomes of stereotactic body radiotherapy (SBRT) for operable patients with early-stage non-small cell lung cancer (NSCLC) and to evaluate factors associated with outcomes. METHODS: We retrospectively analyzed operable patients with NSCLC, staged as cT1-2N0M0, treated with SBRT between 2006 and 2015. Both biopsy-proven and clinically diagnosed NSCLC were included. Local control and survival rates were calculated and compared between subsets of patients. We investigated factors associated with outcomes. RESULTS: We identified 88 operable patients among 661 patients with cT1-2N0M0 NSCLC. The median age was 79 years (range: 55-88). The median follow-up time after SBRT was 40 months (range: 4-121). Fifty-nine patients had been pathologically diagnosed and the other 29 had been clinically diagnosed as having NSCLC. Local control, cause-specific survival (CSS) and overall survival (OS) at 3 years were 91%, 97% and 90% for T1, and 100%, 82% and 74% for T2, respectively. The CSS and OS at 3 years were 100% and 100% for GGO and 83% and 59% for solid tumors, respectively (p=0.005). On univariate analysis, age and T stage were significantly associated with CSS, and age, the Charlson Comorbidity Index (CCI), and opacity were significantly associated with OS. On multivariate analysis, age and CCI were significantly associated with OS. As for toxicities, Grades 0, 1, 2 and 3 radiation pneumonitis occurred in 37.5%, 47.7%, 13.6% and 1.1% of patients, respectively. No Grade 4 or 5 radiation pneumonitis occurred, and no other toxicities of Grade 2 or above were observed. CONCLUSION: Outcomes of SBRT for operable early stage NSCLC were as good as previous SBRT and surgery studies. Further investigation for selecting good SBRT candidates is warranted in high-risk operable patients.

Stereotactic body radiotherapy for T3 and T4N0M0 non-small cell lung cancer.

To evaluate the outcomes and feasibility of stereotactic body radiotherapy (SBRT) for cT3 and cT4N0M0 non-small cell lung cancer (NSCLC), 25 patients with localized primary NSCLC diagnosed as cT3 or cT4N0M0, given SBRT between May 2005 and July 2013, were analyzed. All patients had inoperable tumors. The major reasons for tumors being unresectable were insufficient respiratory function for curative resection, advanced age (>80 years old) or technically inoperable due to invasion into critical organs. The median patient age was 79 years (range; 60-86). The median follow-up duration was 25 months (range: 5-100 months). The 2-year overall survival rates for T3 and T4 were 57% and 69%, respectively. The 2-year local control rates for T3 and T4 were 91% and 68%, respectively. As for toxicities, Grade 0-1, Grade 2 and Grade 3 radiation pneumonitis occurred in 23, 1 and 1 patient, respectively. No other acute or symptomatic late toxicities were reported. Thirteen patients who had no local, mediastinal or intrapulmonary progression at one year after SBRT underwent pulmonary function testing. The median variation in pre-SBRT and post-SBRT forced expiratory volume in 1 s (FEV1) values was -0.1 (-0.8-0.8). This variation was not statistically significant (P = 0.56). Forced vital capacity (FVC), vital capacity (VC), %VC and %FEV1 also showed no significant differences. SBRT for cT3 and cT4N0M0 NSCLC was both effective and feasible. Considering the favorable survival and low morbidity rate, SBRT is a potential treatment option for cT3 and cT4N0M0 NSCLC.

Stereotactic body radiotherapy for patients with oligometastases from colorectal cancer: risk-adapted dose prescription with a maximum dose of 83-100 Gy in five fractions.

We previously reported that the local control of pulmonary metastases from colorectal cancer (CRC) following stereotactic body radiotherapy (SBRT) with moderate prescription dose was relatively worse. We investigated the treatment outcomes and toxicities of patients with oligometastases from CRC treated by SBRT using risk-adapted, very high- and convergent-dose regimens. Among patients referred for SBRT from August 2011 to January 2015, those patients were extracted who had liver or pulmonary metastases from CRC, and they were treated with a total dose of 50-60 Gy in five fractions prescribed to the 60% isodose line of the maximum dose covering the surface of the planning target volume. Concurrent administration of chemotherapy was not admitted during SBRT, while neoadjuvant or adjuvant chemotherapy was allowed. A total of 21 patients (12 liver, 9 lung) with 28 oligometastases were evaluated. The median follow-up duration was 27.5 months (range: 6.5-43.3 months). Four patients were treated with SBRT as a series of initial treatments, and 17 patients were treated after recurrent oligometastases. The local control rates at 1 and 2 years from the start of SBRT were 100%. The disease-free and actuarial overall survival rates were 62% and 55%, and 79% and 79%, respectively. No severe toxicities (≥grade 3) occurred during follow-up. The outcomes following high-dose SBRT were excellent. This treatment can provide an alternative to the surgical resection of oligometastases from CRC. Prospective studies are needed to validate the effectiveness of SBRT.

Influence of liver toxicities on prognosis after stereotactic body radiation therapy for hepatocellular carcinoma.

AIM: To better define clinically relevant non-classic radiation-induced liver disease (RILD) following stereotactic body radiotherapy (SBRT) in patients with small hepatocellular carcinoma (HCC). METHODS: We retrospectively evaluated the influence of acute liver toxicities on fatal hepatic failure in HCC patients treated with SBRT. Between April 2006 and February 2012, 194 HCC were treated with SBRT. Among them, patients followed up for more than 6 months were eligible. Laboratory results and Child-Pugh (CP) scores were obtained before treatment and at monthly follow-up visits. Toxicities were evaluated by the Common Terminology Criteria for Adverse Events version 4.0. Possible definitions of RILD were evaluated with respect to fatal hepatic failure within 12 months. RESULTS: One hundred and eighty HCC were evaluated with a median follow-up of 28.2 months. Fatal hepatic failure within 12 months occurred in eight patients (4%). On univariate analysis, grade 3 or more elevated transaminases, CP score of 8 or more, and/or grade 3 or more decreased platelet count significantly predicted fatal hepatic failure within 12 months. Combinations of these factors (i.e. having at least one criterion) also predicted fatal hepatic failure within 12 months (16% with criteria vs 1% without criteria). Two-year overall survival rates for patients with and without RILD was 64.9% and 83.8% (P < 0.001), respectively. CONCLUSION: We identified three criteria that affected overall survival in HCC patients treated with SBRT. Further prospective studies are warranted to validate the safety and effect of SBRT for HCC.

Toxicities of organs at risk in the mediastinal and hilar regions following stereotactic body radiotherapy for centrally located lung tumors.

INTRODUCTION: We investigated tolerable doses to organs at risk (OARs) in the mediastinum and pulmonary hilum following stereotactic body radiotherapy for centrally located lung tumors. METHODS: Between 2005 and 2012, 381 patients with lung tumors were treated with stereotactic body radiotherapy of 40 to 60 Gy in five fractions. From among these patients, we extracted those who received greater than 25 Gy irradiation to OARs and analyzed dosimetric factors in relation to grade 3 to 5 toxicities. RESULTS: In total, 398 OARs in 133 patients were analyzed, with a median follow-up of 33 (range, 3-87) months. The numbers receiving greater than 25 Gy irradiation to the aorta, vena cava, pulmonary artery, pulmonary vein, bronchus, trachea, heart, and esophagus were 72, 33, 73, 60, 55, 13, 69, and 23, respectively. The corresponding median Dmax 0.5 ml were 43.8, 32.0, 32.2, 29.1, 28.4, 28.7, 41.1, and 21.7 Gy. Of these patients, two developed grade 5 and one grade 3 hemoptysis, and two had grade 3 obstructive pneumonia. Two patients with grade 5 hemoptysis received high doses at the pulmonary artery and bronchus (59.2 and 54.4 Gy, and 61.3 and 59.6 Gy, respectively). No other grade 3 to 5 toxicities occurred. CONCLUSION: Therapeutic indications and dose-intensity should be carefully determined for patients with central tumors, especially when doses to the pulmonary artery and bronchus in the pulmonary hilum exceed 50 Gy. Tolerable doses for other OARs might, however, be higher than in this study, though longer follow-up is necessary to assess this possibility.

Feasibility study of stereotactic body radiotherapy for peripheral lung tumors with a maximum dose of 100 Gy in five fractions and a heterogeneous dose distribution in the planning target volume.

We evaluated toxicity and outcomes for patients with peripheral lung tumors treated with stereotactic body radiation therapy (SBRT) in a dose-escalation and dose-convergence study. A total of 15 patients were enrolled. SBRT was performed with 60 Gy in 5 fractions (fr.) prescribed to the 60% isodose line of maximum dose, which was 100 Gy in 5 fr., covering the planning target volume (PTV) surface (60 Gy/5 fr. - (60%-isodose)) using dynamic conformal multiple arc therapy (DCMAT). The primary endpoint was radiation pneumonitis (RP) ≥ Grade 2 within 6 months. Toxicities were graded according to the Common Terminology Criteria for Adverse Events, version 4.0. Using dose-volumetric analysis, the trial regimen of 60 Gy/5 fr. - (60%-isodose) was compared with our institutional conventional regimen of 50 Gy/5 fr. - (80%-isodose). The enrolled consecutive patients had either a solitary peripheral tumor or two ipsilateral tumors. The median follow-up duration was 22.0 (12.0-27.0) months. After 6 months post-SBRT, the respective number of RP Grade 0, 1 and 2 cases was 5, 9 and 1. In the Grade 2 RP patient, the image showed an organizing pneumonia pattern at 6.0 months post-SBRT. No other toxicity was found. At last follow-up, there was no evidence of recurrence of the treated tumors. The target volumes of 60 Gy/ 5 fr. - (60%-isodose) were irradiated with a significantly higher dose than those of 50 Gy/5 fr. - (80%-isodose), while the former dosimetric parameters of normal lung were almost equivalent to the latter. SBRT with 60 Gy/5 fr. - (60%-isodose) using DCMAT allowed the delivery of very high and convergent doses to peripheral lung tumors with feasibility in the acute and subacute phases. Further follow-up is required to assess for late toxicity.

Stereotactic ablative body radiation therapy with dynamic conformal multiple arc therapy for liver tumors: optimal isodose line fitting to the planning target volume.

PURPOSE: To assess optimal relative prescribed dose values in stereotactic ablative body radiation therapy (SABR) using dynamic conformal multiple arc therapy (DCMAT) for liver tumors. METHODS AND MATERIALS: We generated SABR plans for 8 typical liver tumors that received SABR with 50 Gy in 5 fractions. The prescribed dose had previously been defined as 80% of the maximal dose ("80% isodose plan"). Alternatively, 20%-90% isodose plans were created to compare dosimetric factors. RESULTS: The mean liver volume values (%) that received >20 Gy (V20) and the mean liver dose were both the lowest with a 70% isodose plan and were the second lowest with a 60% isodose plan. The V20 dose was 5.19% lower (11.14%) with a 70% isodose plan and 4.51% lower (11.22%) with a 60% isodose plan compared with the value with an 80% isodose plan (11.75%). Mean planning target volume (PTV) dose increased as the % isodose decreased. The mean PTV dose was 10% higher (62.4 Gy) with a 70% isodose plan and 21% higher (68.9 Gy) with a 60% isodose plan compared with the value with an 80% isodose plan (56.8 Gy). CONCLUSIONS: During SABR treatment planning using DCMAT for liver tumors, target doses increased as the percentage isodose value decreased, which could result in better outcomes. In contrast, a 70% isodose plan had the lowest normal liver dose and a 60% isodose plan had the second lowest. An optimal percentage isodose level might be adjusted depending on tumor radiation sensitivity and liver function reserve. Further investigation is warranted to determine whether these dosimetric advantages result in improved outcomes.

Threshold doses for focal liver reaction after stereotactic ablative body radiation therapy for small hepatocellular carcinoma depend on liver function: evaluation on magnetic resonance imaging with Gd-EOB-DTPA.

PURPOSE: Focal liver reaction (FLR) appears on radiographic images after stereotactic ablative body radiation therapy (SABR) in patients with hepatocellular carcinoma (HCC) and chronic liver disease. We investigated the threshold dose (TD) of FLR and possible factors affecting the TD on gadoxetate acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI). METHODS AND MATERIALS: In 50 patients who were treated with SABR for small HCC and followed up by MRI for >6 months, FLR, seen as a hypointense area, was evaluated on the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI. The follow-up MRI with the largest extent of FLR was fused to the planning computed tomography (CT) image, and patients with good image fusion concordance were eligible. After delineating the border of the FLR manually, a dose-volume histogram was used to identify the TD for the FLR. Clinical and volumetric factors were analyzed for correlation with the TD. RESULTS: A total of 45 patients were eligible for analysis with a median image fusion concordance of 84.9% (range, 71.6-95.4%). The median duration between SABR and subsequent hepatobiliary phase MRI with the largest extent of FLR was 3 months (range, 1-6 months). The median TD for FLR was 28.0 Gy (range, 22.3-36.4 Gy). On univariate analysis, pre-treatment Child-Pugh (CP) score and platelet count were significantly correlated with the TD. On multiple linear regression analysis, CP score was the only parameter that predicted TD. Median TDs were 30.5 Gy (range, 26.2.3-36.4 Gy) and 25.2 Gy (range, 22.3-27.5 Gy) for patients with CP-A and CP-B disease, respectively. CONCLUSION: The TD was significantly correlated with baseline liver function. We propose 30 Gy for CP-A disease and 25 Gy for CP-B disease in 5 fractions as TDs for FLR after SABR for patients with HCC and chronic liver disease. Use of these TDs will help to predict potential loss of liver tissue after SABR.